Distillate field production



Sept. 5, 1 944. c. F. TEICHMANN DISTILLATE FIELD PPRODUCTION Filed Oct.51, 1942 m NT Patented Sept. 5, 1944 DISTILLATE FIELD PRODUCTION CharlesF. Teiehmann, Mount Vernon, N. Y., as-

signor to Texaco Development Corporation, New York, N. Y., a corporationof Delaware Application October 31, 1942, Serial No. 464,118

6 Claims. (Cl. 166-21) 1 Thi invention relates to the production ofhydrocarbons from underground formations and more particularly to aprocess for the production of a certain class of distillate orcondensate formations.

It is now well-known that the hydrocarbons present in the producingformations of distillate or condensate fields exist therein the form ofa appears that the formation fluid constitutes a single homogeneousphase which is usualy substantially at the dew point. Thus, upon anyreduction in temperature and/or pressure, condensation of hydrocarbonstakes place. The condensation of hydrocarbons taking place upon areduction in pressure is recognized as being due to the operation of thenow familiar phenomenon of retrograde condensation.

When flowing a distillate fluid from the formation to the surface, thereduction in pressure and temperature that necessarily occurs iseffective to cause the condensation of an important part of theliqueflable hydrocarbons contained in the distillate fluid. The liquidand gas phases formed in this way are generally composed predominantlyof the same hydrocarbons, but the liquid phase contains a much higherproportion of the heavier hydrocarbons than was present in the originalfluid, while the gas phase has a higher proportion of the lighterhydrocarbons. Accordingly, by controlling the condensation due totemperature 1 drop and the condensation due to the retrograde the otherhydrocarbons have decreased in value for the time being. The lessvaluable hydrocarbons, therefore, have presented in many cases merely astorage problem. In the case of distillate fluids, in some-localities,the pentanes,

butanes, and propane are valuable compounds for use in alkylationreactions and other processes, while the remaining hydrocarbons aredistinctly less valuable. It would be desirable in these cases toproduce only the valuable hydrocarbons and to leave the remaininghydrocarbons for later production. However, so far as known, no meansfor accomplishing thi has been pro Posed As stated above, distillateformations are usu- 'ally found at great depths.

These formations may be located below partially or. substantiallydepleted oil formations or oil formations containing an insuflicientamount of oil to be produced emciently. Oil formations of this-type arereferred to hereinafter, generically, as formations having a. lowcontent of oil.

The present invention is concerned with situations where there is a deepdistillate formation and above the distillate formation a formationhaving a low content of oil. The principal object of the invention is toprovide a process for the production of such a distillate formation bywhich desired lighter hydrocarbons may be recovered at the surface, andheavier hydrocarbons may be stored under conditions such that they maybe produced at a later date.

With this object in view, the proces of the invention comprises flowingthe distillate fluid from the distillate formation to the upperformation having a low content of oil, depositing condensed heavierhydrocarbons in the oil formation, and removing lighter hydrocarbons ofthe distillate fluid from the oil formation. All or part of theselighter hydrocarbons may be used at the surface. Where no other meansfor maintaining pressures in the distillat formation are available,however, it is usually essential to separate the lightest hydrocarbons,such as the methane and ethane, and return these after compression tothe distillate formation. The oil formation, therefore, is used as acombination separator and storage vessel, and the separated hydrocarbonsmay be produced from the oil formation by normal methods at any timethis becomes desirable.

In order to carry out the present process there should be provided oneor more producing wells bottomed in the distillate sands and havingmeans such as perforated casing for conducting the distillate fluid fromthe interior of the distillate well bore into the upper oil sand. so,there should be provided one or more well equipped so as to produce onlyfrom the upper oil sands. Iniection wells should also be provided so asto introduce a repressuring medium, usually residual gases, into thedistillate formation. With this arrangement of wells the distillatefluid is permitted to flow up the distillate well to the'oil sand,through the oil sand to the well producing from this sand, and thence upthis wellto the surface. At the surface the desired hydrocarbons may berecovered and those not utilized may be compressed and returned throughthe injection well to the distillate formation,

It will be understood that the temperature and pressure of the fluidwill be reduced in flowing from the distillate formation to the upperoil sand and that condensation of hydrocarbons will occur. Additionalreduction in temperature and pressure, resulting in furthercondensation, will be accomplished in the passage from the distillatewell through the oil sand. These condensed hydrocarbons will separateout in the oil sand and may be recovered later by the usual productionmethods.

In Order to'accomplish the objects of the present invention efllciently.a number of factors should be taken into consideration. These factorsare the pressure and temperature conditions in the distillate formation,the composition of the distillate fluid, the distance between thedistillate formation and the upper oil sand, the temperature of theupper oil sand, the permeability of this sand, the distance between thedistillate wells and the wells leading from the oil sand, and the rateof flow of the distillate fluid. These factors should be adjusted andcontrolled so as to obtain at the bottom of the well leading from theupper oil sand, temperature and pressure conditions at which the desiredseparation between liquid and gas phases may be accomplished. Forexample, in the case where the distance between the distillate formationand the upper oil sand is not as great as could be desired, this may becompensated for by locating the wells leading from the upper oil sand ata greater distance from the distillate wells. Thus, the drop in pressurein the oil sands will be increased so as to reach the desired pressureat the bottom of the wells leading from the oil sands. The temperatureand pressure which should be obtained at the bottom of the wells leadingfrom the oil sands cannot be stated for a particular case because of thevarying characteristics of distillate fluids, and the fact that it maybe desirable to accomplish different types of separation in differentfields. It may be stated, however, that in general, where the process isto be operated so as to make a rough separation between the hexanes andheavier hydrocarbons and the pentanes and lighter-hydrocarbons thepressure should lie within the range from about 1,500 to 3,000 poundsper square inch and the temperature within the range from about 100 to200 F., the particular conditions within these ranges which are optimumin a given case being dependent upon the composition of the fluid.

In order that the invention may be understood more fully, referenceshould be had to the accompanying drawing in which the single figurerepresents in diagrammatic form a distillate field equipped to carry outthe present process. A distillate formation is represented generally atA, and lying a substantial distance above this formation, separated by anumber of other strata such as B" and C, is an oil formation D having alow oil content. A well I0, which is repre sentative of a number of suchwells, is shown bottomed in distillate formation A. This well isprovided with a casing I2. When carrying out the present process thedistillate fluid flows through perforations [4 in casing l2 into well land passes up the well to the oil formation D. Just above the oilformation there is preferably provided in the well ID a means, such aspacker 16, adapted to prevent the flow of fluid up the well. Oppositethe oil formation the casing I2 35 pressor 34.

is perforated as shown at l8. The fluid, therefore, flows through theseperforations and into the oil formation.

Bottomed in the oil formation is another well 5 20, which also isrepresentative of a number of such wells. The distillate fluid,therefore, passes through the oil sand into well 20 and through thiswell to the surface. The hydrocarbons condensed due to the reduction intemperature and pressure between the distillate formation and the bottomof well 20 are separated from the remainder of the fluid and collect inthe oil sands. The remainder of the distillate fluid which, flows fromthe well 20 is passed intovalved line 22 leading to a recovery systemindicated generally at 24. Since the particular method of recoverlniihydrocarbons does not form apart of the present invention no attemptwill be made to describe this system in detail. In general, the systermwill preferably include an absorber in which the fluid is contacted witha suitable absorption oil, which removes therefrom the hydrocarbons tobe recovered, preferably the pentanes, butanes and propanes. Thesehydrocarbons may be re- 5 moved to storage through valved line 28. The

recovery system, of course, may also include steps whereby closer cutfractions are obtained.

When carried out in the usual manner the process will comprise removingresidual gases,'

40 late reservoir.

In order to disclose the invention more-fully the following specificmanner of carrying out the process of the invention will be described.In this case the process is used for the production of a distillateformation which is at a depth of about 10,000 feet and in which thepressure is about 4,800-pounds per square inch and the temperature about235 F. The composition of the distillate fluid is such'that theseconditions of temperature and pressure are substantially those at thedew point for the fluid. when flowed at a normal rate from thedistillate formation to the upper oil formation, which in this case isat a depth of about 3,000 feet, the pressure and temperature conditionsof the fluid on entering the oil sands may be about 3,700 pounds persquare inch and about 190 to 200 F. Under these conditions thedistillate fluid is a two-phase product. The fluid enters oil formationD and passes to well 20. Due primarily to the effect of friction, thepressure on the fluid is further reduced and in this case, on theassumption a rough fractionation to separate hexanes and heavier fromthe pentanes and lighter is desired, the distillate fluid is flowed atsuch a rate and the well 20 is placed at such a distance from theproducing well ID as to cause the fluid to enter the well 20 at apressure of about 2,200 to 3,000 pounds per square inch. Since the oilformation may be at a temperature of about 135 F. additional cooling ofthe fluid will be produced by the passage through the oil formation.

Thus, the fluid passing up well 20 will consist largely of hydrocarbonscontaining five or less carbon atoms. This fluid is then flowed throughvalved line '22 to the recovery system and treated as described above.The deposited hydrocarbons will flow'by gravity slowly downwardly in oilformation D. These hydrocarbons may be recovof the invention, ashereinbefore set forth, may

be made without departing from the spirit and scope thereof, andtherefore only such limitations should be imposed as are indicated inthe appended claims.

I claim: I 1. The process of producing a distillate formation locatedbelow a formation which has a low content of oil and which is'atpressure and temperature conditions below the dew point of thedistillate fluid, which comprises flowing said distillate fluid upwardlythrough a well tapping the distillate formation to a point opposite theoil formation, the conditions of temperature and pressure on the fluidat said point being lower than the conditions of temperature andpressure in said distillate formation, passing the distillate fluidthrough said oil formation to a well tapping temperature conditionsbelow the dew point of the distillate fluid, which comprises flowingsaid distillate fluid upwardly through a' well tapping the distillateformation to a point opposite the oil formation, the conditions oftemperature and pressure on the fluid at said point being lower than theconditions of temperature and pressurein said distillate formation,passing the distillate fluid through said oil formation to a welltapping the oil formation, separating out in said oil formationcondensed hydrocarbons formed from said distillate fluid, recoveringdesired hydro-- carbons from said remainder of said distillate fluidleaving residual gases, compressing residual gases, and returning saidcompressed residual Cases to said distillate formation to maintainformation pressures.

3. The process of producing a distillate formation located a substantialdistance below a.

formation which has a low content of oil and which is at temperature andpressure conditions below the dew point of the distillate fluid, whichcomprises flowing the distillate fluid from said distillate formationinto a well tapping said formation and communicating with said oilformation. passing the distillate fluid up said well and into said oilformation, separating out in said oil formation condensed hydrocarbonsformed in said "distillate fluid due to the difference in the conditionsof temperature and pressure on the distillate fluid in said distillateformation and in said oil formation, flowing the remainder of I saiddistillate fluid into a well tapping said oil formation, passing saidremainder of said distillate fluid through said well tapping said oilformation to the surface, and recovering desired hydrocarbons from saidremainder of said distillate fluid, the location of said well tappingsaid oil formation being so selected in relation to the location of saidwell tapping said distillate'formation as to produce temperature andpressure conditions on the distillate fluid in said oil formationadapted to accomplish a selected condensation of hydrocarbons from saiddistillate fluid.

4. A process in accordance with claim 3 in which residual gasescomprising methane and ethane are separated from said remainder of saiddistillate fluid and said residual gases are compressed and returned tosaid distillate formation to maintain formation pressures.

5. The process of producing a distillate formation located a substantialdistance below a formation which has a low content of oil and which isat temperature and pressure conditions below the dew point of thedistillate fluid, which comprises flowing the distillate fluid from saiddistillate formation into a well tapping said formation andcommunicating with said oil formation, passing said distillate fluid upsaid well and into said oil formation, separating out in said oilformation condensed. hydrocarbons consisting predominantly of hexanesand heavier hydrocarbons formed in said distillate fluid due to thedifference in the conditions of temperature and pressure on saiddistillate fluid in said distillate formation and in said oil formation,flowing the remainder of the distillate fluid consisting predominantlyof pentanes and lighter hydrocarbons into a well tapping said oilformation, passing said remainder of said distillate fluid through saidwell tapping said oil formation to the surface, and recovering desiredhydrocarbons from said remainder of said distillate fluid, the locationof said well tapping said oil formation being so selected in relation tothe location of said well tapping said distillate formation as toproduce temperature and pressure conditions on the distillate fluid insaid oil formation adapted to accomplish selective, condensation ofhexanes and heavier hydrocarbons from said distillate fluid.

6. The process of producing a distillate forma-- tion located asubstantial distance below a formation which has a low content of oiland which is at temperature and pressure conditions below the dew pointof the distillate fluid, which comprises flowing the distillate fluidfrom said distillate formation into a well tapping said formation andcommunicating with said oil formation, passing said distillate fluid upsaid well and into said oil formation, separ ing out in said oilformation condensed hyd ocarbons consisting pre-.-

dominantly of hexanes and heavier hydrocarbons formed in said distillatefluid due to the diiference in the conditions of temperature andpressure on the fluid in said distillate formation and in said oilformation, flowing the remainder of the distillate fluid consistingpredominantly of pentanes and lighter hydrocarbons into a well tappingsaid oil formation, passing said remainder of said distillate fluidthrough said well tapping said oil formation to the surface, andrecovering desired hydrocarbons from said remainder of said distillatefluid, the location of said well tapping said oil formation being soselected in relation to the location of said well tapping saiddistillate formation as to-produce atemperature of about to 200 F. and apressure of about 1,500 to 3,000 pounds per square inch on thedistillate fluid in said oil formation adapted to accomplish selectivecondensation of hexanes and heavier hydrocarbons from said distillatefluid;

CHARLES F. 'I'EICIMANN.

